1. Field of the Invention
This invention relates to propellants and is particularly directed to gun propellant formulations employing a copolymer of polyglycidyl azide (GAP) and nitrocellulose (NC) to provide low isochoric flame temperatures and high mass impetus.
2. Description of the Prior Art
Considerable advances have been realized in the area of improved gun propellants during the last ten years. The conventional gun propellants described in U.S. Army Propellant Manual No. AMCP-706-150, published February 1965, are based upon nitrocellulose, nitroglycerin (NG), and nitroguanidine (NQ).
Improvements in performance over those listed in Manual No. AMCP-706-150 have been made by incorporating triaminoguanidine nitrate (TAGN) and cyclotetramethylene tetranitramine (HMX) into the basic nitrocellulose matrix as described in U.S. Pat. Nos. 3,732,130; 3,732,131 and 3,909,323.
However, while the advanced propellants based upon TAGN/HMX/NC yield higher performance, these propellants generally contain more of the solid oxidizers (TAGN and HMX) on a weight basis than the binder (NC). This, in turn, can lead to erratic ballistics at extreme weather conditions where the propellant is subjected to very low temperatures (less than -25.degree. F.). Due to the low level of polymer (binder) present, the propellant can become brittle and crack, thereby exposing larger areas for instantaneous burning. This results in overpressures in the gun breech.
In a similar manner, propellants which are to be inhibited according to U.S. Pat. No. 3,948,697 must rely on the residual hydroxyl groups in nitrocellulose for superior surface bonding. Incorporation of plasticizers which contain additional hydroxyl groups, such as polyethelene glycol, drastically lower the overall propellant performance since the heat of formation of the plasticizer is degraded by hydroxyl moieties.